uint8 STOP = 0
uint8 READY = 1
uint8 PUSH = 2

uint8 SPEED_ZERO_FOR_TEST = 0
uint8 SPEED_10M_PER_SECOND = 1
uint8 SPEED_15M_PER_SECOND = 2
uint8 SPEED_16M_PER_SECOND = 3
uint8 SPEED_18M_PER_SECOND = 4
uint8 SPEED_30M_PER_SECOND = 5

uint8 mode
float64 wheel_speed
float64 hz
time stamp
